Telecommunications networks include backbone networks having the main voice and data switches and access networks that carry traffic from the main voice and data switches out to business and residential subscribers. Historically, access networks have carried either voice traffic or data traffic converted into a voice format through modems and similar devices. With the advent of the Internet, the majority of data traffic is now carried in Internet Protocol (IP) packets.
Transporting data natively as IP packets using IP routing, however, requires extensive messaging and configuration overhead. High capacity IP routing can be efficiently implemented with hardware-based solutions in the backbone network due to the large economies of scale. Low capacity IP routing can also be efficiently implemented at customer premises using software-based routing solutions that exploit the low cost of microprocessors. IP routing, however, cannot be efficiently implemented in the intermediate speed access network where neither economies of scale nor low cost microprocessors can be exploited.
Recent developments in access networks have included the incorporation of asynchronous transport mode (ATM) functionality in access equipment. ATM switching equipment is relatively inexpensive compared with IP routers, which is a primary consideration in access networks due to the wide distribution of access equipment. The overhead of ATM cells (5 bytes for every 48 bytes of payload), however, makes ATM less attractive as a transport technology.